British light heavyweight Joshua Buatsi earned a win yet disappointing debut to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a split decision in a close ten-round contest at the Co-op Live Arena.
But Parker found success, connecting with powerful clean blows in a contest where the techniques never quite clicked, with excessive holding marring the action.
Two judges had it 96-94 for to Buatsi, with the final judge a 95-95.
"It wasn't my greatest display but what do champions do? They prevail," Buatsi commented in the ringside as he was met by boos from the crowd.
The British fighter returned to winning ways after his first professional defeat - an epic battle with his previous opponent in February - to claim a 20th career victory.
Some ringside observers thought the challenger, 31, should have been awarded the victory but the contender endured the second loss of his 28-bout professional journey.
The Champion Claims Victory in Dull Match
His career development has stalled in the past few years through management issues and considerable time of inactivity.
Once tipped as the next star of the British fight scene, he now finds himself trying to achieve expectations - possibly in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter willing to overcommit in a cagey initial rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second appearance at the higher weight class.
By the middle rounds, Parker had stayed in contention, making life awkward for Buatsi, who operated with a solid defense to edge the cleaner periods.
The audience's tolerance decreased because of constant clinching, with Parker slipping to the canvas multiple occasions during close exchanges.
The underdog finished the stronger, but multiple periods were challenging to assess. However, ex-champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just a single round.
The victor progresses, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - on this evidence - still appears challenging.
Hatton Memorial Inspires Manchester Derby Contest
In the secondary fight, Lyndon Arthur defeated Rea by divided decision in a terrific Manchester vs Manchester battle to win the European light-heavyweight title.
The arena became quiet for a extremely emotional homage ahead of the contest as ten bells sounded in remembrance of local hero Ricky Hatton, who died at age 46 in last month.
It was the first major televised match card in the urban center since Hatton's passing. As the concluding sound faded, the quiet became a shout of "there's only one Ricky Hatton".
The competition inside the ropes matched the feeling. The eventual winner was floored by a powerful punch flush on the chin in the second round, standing uncertainly to his position on the eight count.
But the red-colored equipment of Arthur soon pressed ahead again. From the other corner, the opponent - in competitive blue - was marked up quickly, significant bruising appearing under his eye as the pair traded punishing blows.
The challenger, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with stinging uppercuts as the action rarely dropped over the full distance.
The victor narrowly won the result with scoring tallies of even score, narrow lead and wider gap, but the two athletes were persistent and courageous, everything their idol Hatton stood for.
